Methods control systems for viscosity and density control may include a frequency loop shaping filter for shaping the frequency response in real-time for a multiple inputs multiple outputs (MIMO) system. For example, a method may include drilling a wellbore while circulating a drilling mud through a viscosity and density control system that includes one of: a mechanical separation system, a dilution system, a chemical additive regulation system, and any combination thereof; applying a frequency loop shaping filter to a desired mud viscosity and a desired mud density to produce control signals: a first control signal for the mechanical separation system, a second control signal for the dilution system, a third control signal for the chemical additive regulation system, and any combination thereof; and applying the control signals to the corresponding systems to alter the drilling mud to have a controlled viscosity value and a controlled density value.